DESCRIPTION: This investigator has identified a novel gene, cdc12, in S. pombe that appears to play an important role in the assembly and placement of the contractile ring. He hypothesizes that during interphase, cdc12 exists in a large multiprotein complex that travels along microtubules to the middle of the cell to mark the future site of the cleavage furrow. During mitosis, the cdc12 protein is hypothesized to participate in actin ring assembly through an interaction with the actin-binding protein profilin. Dr. Chang's immediate goal is to test these hypotheses. Three specific aims are proposed: (1) to determine the function of the interaction between cdc12 and cdc3 (profilin); (2) to identify and characterize additional proteins that interact with cdc12p; and (3) to investigate the spatial aspects of ring formation by examining ring formation in living cells.